1. Field of the Invention
The invention relates to a system usable with a pipe laying vessel, comprising:                a support frame, such as a deck frame of the vessel,        a loader arm which is pivotable between a loading position and a laying position, which loader arm is provided with a pipe section manipulation system,        a first clamping member having a substantially fixed position with respect to the support frame, which first clamping member is operable between a clamped position for supporting the weight of a pipeline extending into the sea, and a released position for allowing the pipeline to be lowered with respect to the first clamping member,        a second clamping member being movable between an upper position and a lower position, which second clamping member is operable between a clamped position for supporting the weight of the pipeline during movement from the upper position to the lower position, and a released position for moving the second clamping member from the lower position to the upper position.        
2. Description of the Related Art
A J-lay pipe laying vessel is known. The vessel has a J-lay tower and a loader arm that is pivotable with respect to the J-lay tower between a loading position and an upright position. In its loading position a pipe section is loaded from a pipe storage onto the loader arm, after which it pivots to the upright position adjacent to the J-lay tower. The J-lay tower comprises a system for manipulating the orientation of the pipe section. Thus, the pipe section is brought into alignment with a pipeline extending into the sea. The J-lay tower also has a fixed clamp and a moving clamp that can be operated according to the hand-over-hand principle by intermittently holding the pipeline by the fixed clamp and the moving clamp, respectively. The known J-lay tower is often relatively heavy and not suitable to easily retrofit existing vessels with J-lay equipment.
U.S. Pat. Nos. 6,910,848 and 6,213,686 disclose a system for laying a pipeline from a floating vessel onto the sea floor. This system comprises a J-lay tower with a pipeline extending below the J-lay tower around a bend and onto the sea floor. The J-lay tower has a mast, a working table and a travelling table. The working table and all parts attached to the working table including the mast can be gimballed. The travelling table has a clamp section for clamping the pipeline and can be moved between an upper and lower position. An erector is connected to the working table by a hinge. A new pipe section is loaded on the erector, which is provided with clamps for securing the pipe section to the erector. Then, the erector is pulled up to the mast of the J-lay tower by a cable. The mast of the J-lay tower is provided with a centralizer and a straightener. The centralizer is used to align the lower end of the new pipe section with the top of the pipeline for welding. The straightener can push the centre of the new pipe section while the upper and lower ends are restrained by the travelling table and the centralizer, respectively. Thus, this system comprises a J-lay tower and pivotable erector for loading pipe sections up to the mast of the J-lay tower. Transferring a pipe section from the erector to the J-lay tower is relatively complex.